Wiping materials and methods of making the same



Feb. 12, 1963 F. H. SEXSMITH ETAL 3,077,423

WIPING MATERIALS AND METHODS OF MAKING THE SAME Filed Feb. 19, 1960 2 M? T Efifi m Mm P: B i

United rates Patent 3,077,423 WIPING MATERIALS AND METHODS OF MAKING THE SAME Fred H. Sexsrnith, Highland Park, and De Witt R. Petterson, North Brunswick, N.J., assignors to Chicopee Manufacturing Corporation, a corporation of Massachusetts Filed Feb. 19, 1960, Ser. No. 9,912 3 Ciaims. (Cl. 117-143) This invention relates to improved Wiping materials for absorbing and holding oleaginous substances and to novel methods of making the same. More particularly, the present invention relates to wiping materials for absorb ing and removing oil and grease from surfaces and to novel methods of treating Wiping materials to increase their oil and grease absorption and retention properties.

Oil wiping materials have been used hitherto, for example, in machine shops, garages, and the like, where oil and grease is used and wherein the need arises for wiping materials capable of quickly absorbing the oil or grease and holding it in the wiping material so that it does not redeposit on the surface wiped or transfer to the wipers hand.

Woven textile wiping materials such as the well-known buck towel have been used hitherto on a rental basis but the high initial cost of such materials, plus the cost of pick-up, cleaning and return for re-use, when added to the accidental loss or deliberate pilferage problems, have militated against the complete economic acceptance thereof. Waste materials in the form of clumps of matted threads or shredded fabrics have been used and are satisfactory insofar as oil and grease absorption and retention are concerned, provided the threads are predominantly cotton. The presence of synthetic fibers, however, reduces the oil and grease absorbency considerably. Additionally, such waste materials are not strong and create a lint problem. And, finally, in many cases, they contain grit, dirt and Waste materials which scratch the surfaces being wiped and cut the hands of the person doing the wiping. Disposable paper products have also been used but normally are deficient in their hand and conformability, as well as in their oil and grease absorbency and retention and have not found commercial acceptance.

Efforts to treat such wiping materials having low oil and grease absorbency and retention properties with known highly oleophilic coatings have not led to the expected increase in oil and grease absorbency and retention and such coating efforts have largely been discarded by the industry.

Other materials have had passable oil and grease ahsorbency but have had substantially no water or aqueous media absorbency at all. As a result of such zero acceptance for Water which is often present to a low degree with oil and grease, such other materials have not been found completely acceptable.

It has now been discovered that the oil and grease absorbency and retention of wiping materials may be markedly increased by adhering thereto slightly hydrophilic, strongly oleophilic oil and grease absorbent substances which have been dispersed into very small, crumbly, curdy particles within a predetermined size range.

The slightly hydrophilic, strongly oleophilic absorbent substances used in the application of the present invention are synthetic organic compounds having a relatively long chain length and high molecular weight, along with a balanced afiinity for water and for oleaginous substances. Thermoplastic compounds are preferred for the absorbent substances but thermosetting compounds, it in an initial or intermediate condensation stage, or still solvent-soluble, may also be used. An outstanding memher of such a group is nylon, a long chain, high molecular weight poly-amide resin, and such will be used as illustrative but not limitative of the absorbent substances of the present invention.

The required balanced afiinity for water and oleaginous substances is satisfied when the moisture regain of the selected absorbent is relatively low. However, the moisture regain should not be that low that substantially no hydrophilic properies are present and should not be that high that the hydrophilic properties approach or are equal to or greater than the oleophilic properties. Within the broader aspects of the present invention, a moisture regain at 21 C. and 65% relative humidity for the absorbent material while still in crystalline or partially crystalline form prior to use within the present inventive concept of from about 2.5% to about 8% by weight has been found acceptable for the absorbent materials. Within the more specific aspects of the present invention, a moisture regain for such crystalline or partially crystalline materials of from about 4% to about 6.5% by weight have been found preferred, with optimum values being obtained in the range of from about 4% to about 4.5% by weight.

After the absorbent substances have been deposited on the wiping material and the solvent or other carrier used to solubilize it removed, it is to be noted that the absorbent substance has taken on an amorphous form in which form the moisture regain increases due, most likely, to the increased surface area present. In such amorphous form, the moisture regain is in the range of from about 3% to about 10% at 21 C. and 65 relative humidity, with preferred ranges extending from about 4% to about 8%, with optimum values being noted between about 4% and about 6%.

The amorphous nature of the deposited absorbent substance leads to many of the advantageous properties of the present invention. In such a form, the substance is massed together in non-crystalline lumps in which there is no ordered arrangement. Such an amorphous nature may be obtained Within the principles of the present invention by solubilizing the desired absorbent substance in a selected solvent media or other carrier and then coagulating and precipitating or regenerating the absorbent substance in situ on the wiping material under controlled conditions. During such solubilization and subsequent coagulation, precipitation and regeneration, techniques are employed whereby the amorphous substance being precipitated is dispersed into very small curds or particles of a crumbly, stringy or spongy nature whereby the benetits and advantages of the present invention are realized.

The smallness of the curds or particles, plus their amorphous crumbly and spongy nature, greatly increases the surface area of the absorbent materials and consequently its absorbency is accordingly increased, in very much the same way that the absorbency of asponge is superior to a solid material of the same general size and shape. As a general rule, the smaller the particle size, the greater is the absorbency provided the particles are not that small as to create a dusting problem. Average particle size in the general range of from about 20 microns to about microns have been found satisfactory, with a preferred range being noted from about 20 microns to about 60 microns.

Average particle size is a diflicult measurement to evaluate inasmuch as the curds or particles are very rarely spherical but are actually very irregularly formed in practically all cases. A representative cross section taken at right angles to the long direction of the textile material (see FIG. 1) should therefore beselected and made the subject of aphotomicrograph. Actual physical measurements of a representative group of particles '3 should then be taken and average diameters determined. Several lines or chords passing through the geometric center of the particles should be drawn, measured and averaged. The over-all average of a representative group of curds or particles is the average particle size.

In the accompanying drawing and following specification, there is illustrated and described a typical improved Wiping material prepared by the novel methods of the present invention. It is to be understood, however, that the invention is not to be considered limited to the constructions disclosed except as determined by the scope of the appended claims. Referring to the accompanying drawing:

FIGURE 1 is a schematic, fragmentary showing of a nonwoven fabric which has been treated by the methods of the present invention; and

FIGURE 2 is an enlarged cross-section of the nonwoven fabric of FIGURE 1, taken on the line 2-2. in the direction of the indicating arrows. FIGURE 2 is drawn to a magnification of 270x. The nonwoven fabric, the fibers thereof, and the amorphous polyamide deposited thereon, are identified by appropriate descriptive legends.

The wiping material used as a base or carrier for the dispersed absorbent particles is preferably a textile material made of cloth, paper or other sheet-like materials having a textile hand. It should be soft, conformable and drapable, have a bulky feel, and be capable of being folded or formed into shapes adaptable to the surface being wiped. Chemical resistance to oils, fats and greases is, of course, very important. Strength, both tensile and tear, are desirable but are secondary considerations.

Woven, knitted and crocheted fabrics are well-suited as the base wiping material. Felts, garnets, and nonwoven fabrics are similarly well-suited and have economic advantages. Paper products, especially when reinforced with scrim, gauze, or thread structures, are suitable, provided they are sufficiently soft and conformable. The weight of such base materials will vary, according to the needs and requirements involved. Weights as low as 200 or 220 grains per square yard have been found suitable for light duty purposes whereas other weights up to 4000 grains or more per square yard have been found suitable for heavy duty purposes. Within the more commercial aspects of the present invention, a weight range of from about 600 to about 1100 grains per square yard has been found most in demand.

The fibrous materials used in fabricating the wiping materials may be selected from a wide variety of commercially available fibers. The presence of some hydrophilic behavior in the fibers has been found advantageous in many cases. Cotton and viscose rayon are generally preferred for reasons of low cost and readiness of supply. Other fibers, both natural and synthetic, including wool, silk, nylon, cellulose acetate, polyesters, acrylics, modacrylics, polyolefins, vinyls, azlons, etc., may also be included. Mixtures and blends of such fibers in substantially any proportion may be used. It must be remembered, however, that the fibrous materials used must not be deleteriously affected by the absorbent substance to be applied or by the carrier or solvent by means of which the absorbent sustance is being applied.

The amount of absorbent substance which is applied to the base wiping material will vary according to the desired improvement in oil and grease absorption and retention. As little as add-on based on the weight of the base wiping material has been found to enhance the oil and grease absorption and retention properties. Up to 45% add-on by weight may be applied and is desired in cases where high absorption and retention is desired or required. Greater than 45 add-on by weight is possible but introduces economic factors which militate against such add-ons except in exceptional cases where the increased absorption and retention is necesasry. Preferred limits for the amount of absorbent to be applied to the initial fibrous material are in the range of from 20% to about 35% by weight based on the weight of the initial fibrous material. v

Polya-mides have been found to be especially suitable as the absorbent substances and will be used to further describe the present invention. This, of course, is for illustrative purposes and should not be construed as limitative of the inventive concept. Any form of polyamide nylon commercially available is suitable and such would include nylon-6/6 (hexamethylene-diamine-adipic acid), nylon-6/l0 (hexamethylene-diamine-sebacic acid), nylon-6 (poly-caprola-ctam), nylon-l1 (ll-amino andeeanoic acid), etc.

The nylon is dissolved in any suitable solvent therefor, such as a mineral acid, preferably hydrochloric acid or sulfuric acid, or by other solvents for nylon. The presence of an oxygen-containing lower aliphatic compound is advisable to prevent phase separation and to increase solution stability. Examples of such oxygen-containing lower aliphatic compounds are ethylene glycols, diethylene glycol, triethylene glycol, propylene glycol, glycerol, erythrol, erythritol, ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, etc. Such oxygen-containing lower aliphatic compounds may be used in amounts ranging from about 6% to about 40% by weight based on the weight of the nylon solubilizate.

If this freshly solubilized nylon is then directly precipitated on a textile material, such as by being promptly immersed in water at room temperature, the nylon will normally precipitate out as a continuous film on the textile material. Such a continuous film of nylon has been found to possess inferior properties for absorbent purposes and such procedures have been found unsatisfactory for the purposes of the present invention. It is to be appreciated that the term continuous film is not to be construed as limited to the formation of a continuous glass-like sheet of material which completely encases the basic textile material. It is intended to cover structures in which the individual fibrous strands or yarns are more or less continuously covered or coated, so as to prevent the free access of other substances thereto.

In some instances, it is noted that the continuous coating of nylon, which is precipitated as described in the preceding paragraph, breaks up to some extent and a fiocculent or granular precipitate is occasionally obtained. Such a precipitate possesses absorbent properties superior to the continuous film but nevertheless is still considered unsatisfactory for the purposes of the present invention.

It has been found that the solubilized nylon mustibe treated in such a way so that it is broken up and. dispersed into very small curds or crumbly particles. This may be accomplished, according to one method of the present invention, by merely permitting the solubilized nylon to age whereby it will degrade and form crumbly, stringy curds and small particles naturally when it is ultimately coagulated and precipitated.

The amount of time required for the solubilized nylon to break down into the desired small curd or particle size form depends to a large extent upon the constituents of the nylon solution, the relative concentrations of the constituents thereof, the temperature of the solution, etc. Within the broader aspects of the present invention, a holding time of as little as 12 hours has been found to exercise an improving effect. A holding time of as long as about 6 or 7 days has been found to degrade the nylon to an extremely small particle size. holding times may be used but reduce the nylon to such a fine particle size that dusting problems are created. Within the more specific commercial aspects of the present invention, a holding time of from about 48 hours to about hours at room temperature (70 F.) has been found preferable, with optimum results being obtained for holding periods of from about 72 hours to about,

96 hours. It is to be appreciated that these tempera- Longer enemas tures and times are interdependent. That is to say, if the holding temperature is increased, then the holding time may be decreased, and vice versa.

If desired, the dispersing process may be accelerated by employing another method of the present invention, namely, by omitting the aging step and including a blowing or foaming agent such as soda ash in the coagulating and precipitating bath whereby the subsequent bubbling and foaming action due to the reaction between the soda ash and the acidic components of the nylon solution break down the nylon into the desired particle size. Although the use of soda ash is preferred to provide the foaming action, it is to be appreciated that any carbonate or any carbon dioxide gas-producing materials may be used. The use of azo-bis or other organic compounds capable of producing nitrogen gas is also possible. Mechanical blowing, such as by the evaporation of a low-boiling liquid such as fluorocarbon, is also feasible.

The concentration of the soda ash or other blowing agent in the coagulating and precipitating bath may be varied within wide limits depending upon the nature of the blowing agent itself, and upon the degree of bubbling and foaming action desired. From about 5% to about 30% of a basic material has been found satisfactory. The temperature of the foaming bath is preferably elevated say, about 80 C. to about 100 C., whereby its foaming action is more rapid and more energetic.

Subsequent to deposition and formation of the amorphous nylon on the textile material, conventional washing, heating and drying processes take place. The heating of the treated wiping materials should be in the range of from about 80 C. to about 105 C. and should not be that severe as to begin to coalesce or fuse the crumbly, curdy absorbent materials deposited on the textile material.

In cases where the initial fibrous material is of such a nature that is not self-sustaining or is not sufficiently strong as to provide for rapid commercial handling, it is usually preferably pre-bonded with any suitable binder prior to the application of the nylon solubilizate. Any suitable binder which is not deleteriously afiected by the nylon solubilizate can be used. Typical examples are polyvinyl chloride or polyvinyl acetate emulsions, insolubilized starches, viscose, phenoland amine-aldehyd-e condensation products and the like. The amount of pro-bonding agent which is applied may be varied u'within wide limits depending upon circumstances but normally from about 30 grains to about 100 grains per square yard has been found sufficient. The amount of binder must be suflicient to allow for the further process ing of the fibrous material but should not be that much as to interfere with the subsequent deposition of the oil and grease absorbent substances. The pre-binder may be applied in any desired fashion but is preferably intermittently printed in island-bonding fashion.

The invention will be further illustrated in greater detail by the following specific examples. It should be understood, however, that although these examples may describe in particular detail some of the more specific features of the invention, they are given primarily for purposes of illustration and the invention in its broader aspects is not to be construed as limited thereto.

Example I A card web weighing 825 grains per square yard and containing 25% by weight of 1.5 denier, 2-inch staple length viscose rayon fibers and 75% by weight of cotton garnets (approximately /2 to of an inch long) is passed through apparatus illustrated in FIGURE of US. Patent 2,862,251, issued December 2, 1958, and is rearranged into a bundled nonwoven fabric having a square pattern of 18 x 18 holes per square inch. The nonwoven fabric is then intermittently pro-bonded in a pattern of 4 horizontal wavy lines per inch using a carboxymethyl cellulose-thickened polyvinyl chloride emulsion of about 50% solids as the binder. The amount of add-on of the binder is about 75 grains and the lightly pro-bonded nonwoven fabric weighs about 900 grains per square yard after drying.

The dried, pro-bonded nonwoven fabric is then passed through a nylon solubilizate comp-rising 1050 grams of water, 750 grams of sulfuric acid (98%) and 156.5 grams of nylou-6/6. This is equivalent to approximately an 8% nylon solids solubilizate. The nonwoven fabric is impregnated to a 375 %-by-weight wet pick-up (based on the weight of the card web) so that the final fabric will contain about 250 grains per square yard of amorphous nylon. The impregnated fabric is then passed through a 20% solution of sodium bicarbonate in water at C. This solution both coagulates and foams the nylon whereby it assumes a stringy, curdy, spongy amorphous form substantially uniformly distributed in small particles throughout the material. The present moisture regain of the amorphous nylon is determined to be about 5.8%, after 24 hours of conditioning at 65% relative humidity and 21 C. The moisture regain of the base nonwoven fabric is about 7%.

When used as an oil-wiping cloth, the fabric is evaluated by a simple wipe test and scores +10 which indicates a good result.

The simple wipe test is as follows: a 2." x 4" sample of the test Wiping material is folded 4 times to make a l x 2" pad. 5 drops of 30 SAE motor oil are placed on a mirror surface. The oil is wiped first with one side of the pad and then with the other side of the pad. This procedure is repeated, placing 5 drops of 30 SAE on the mirror and again wiping the oil with the sides of the pad in the order of the first trial. The pad is now refolded to expose the clean previously center surfaces to the outside and 2 more trials are made on these newly exposed surfaces, placing 5 drops of 30 SAE on the mirror for each trial, thus making 4 trials in all.

The mate-rials are graded after each trial on three counts: (1) Does the fabric pick up the oil; (2) does the fabric wipe the mirror clean; (3) does the fabric pad, when pressed with reasonable working pressure between the thumb and forefinger, redeposit oil on the forefinger or thumb.

Each of these three counts is evaluated on the same scale where a good score counts +1, a fair score counts 0, and a poor score counts 1. The score is then totaled up for the 4 trials and a marn'mum score on this scale would be +12 and a minimum score would be ---12. For more generic descriptions, materials attaining a score of from 4 to +1 are considered very poor, materials attaining a score of +2 to +4 are considered poor, materials attaining a score of from +5 to +7 are considered fair, and those attaining a score of +8 to +12 are considered good.

Photomicrographic study of the treated wiping materials indicates that the amorphous nylon particles are present in very irregularly shaped, sponge-like shapes having an average diameter or particle size of about 40 microns.

Example II The procedures set forth in Example I are followed substantially as set forth therein with the exception that the sulfuric acid is replaced by an equivalent weight of hydrochloric acid. 14% by weight of ethylene glycol, based on the weight of the nylon solubilizate, is added to enhance stability and prevent phase separation. Additionally, the nylon solubilizate is not passed through a soda ash bath but is aged for 72 hours at :a temperature of 70 F. before being padded on the pre-bonded nonwoven fabric.

The dried nylon-treated wiping material is given a simple wipe test and attains a score of +9 (good). Photomicrographic study of the nonwoven fabric reveals a particle size of the amorphous nylon of about 35 microns.

Example 111 V The procedures of Example II are followed substantially as set forth therein with the exception that the nylon solubilizate is aged for about 96 hours at a temperature of 70 When exposed to the simple Wipe test, a score of is realized. The average particle size of the amorphous nylon is determined to be about 25 microns.

Example IV The procedures of Example I are followed substantially as set forth therein with the exception that the amount of wet pick-up is reduced so that the final fabric contains only 200 grains per square yard of nylon. This is equivalent to an amorphous nylon add-on of about 23.8%. When evaluated by the simple wipe test, the fabric scores +8, thereby indicating a good fabric.

Example V The procedures of Example I are followed substantially as set forth therein with the exception that the amountof wet pick-up is reduced so that the final fabric contains only about 150 grains per square yard of amorphous nylon. This is equivalent to a dry amorphous nylon add-on of about 17.7%, based on the Weight of the initial card web. When evaluated on the simple wipe test procedure, a score of +6 is realized, thus indicating a fair fabric.

Example VI The procedures of Example I are followed substantially as set forth therein with the exception that the Wet pick-up is increased so that the final fabric contains about 450 grains per square yard of amorphous nylon. This is equivalent to about a 53% dry add-on of amorphous nylon. When evaluated by the simple wipe test a fair rating (+7) is attained but it is noted that the use of the too much nylon stiffens the fabric and thereby reduces its wiping efficiency.

As used herein, the term oleaginous is intended to refer to oily, unctuous, liquid or semi-solid materials of an animal, vegetable or mineral nature, whether natural or synthetic in origin. Representativebut not limitative of such materials are: the petroleum mineral oils of pureparafiinic, semiparaffinic, naphthenic or asphaltic base; the cutting fiuids (lubricants and coolants) for machining including mineral, fixed, compounded and sulphurized oils; the greases, basically mineral oils thickened by compounding with sodium, calcium, lithium, aluminum or other soaps; the specially prepared oils including spindle oils, transformer oils, turbine oils, white oils, watch oils, etc.; silicone fluids including silicone greases and silicone oils, etc.; the animal, vegetable and fish oils, fats and esters, edible or inedible, including tallow, tallow oil, lard, lard oil, degras, neats-foot oil, whale oil, sperm oil, castor oil, cottonseed oil, corn oil, rapeseed oil; etc.

Although several specific examples of the inventive concept have been described, the same should not be construed as limited thereby nor to the specific features mentioned therein but to include various other equivalent features as set forth in the claims appended hereto. It is understood that any suitable changes, modifications and variations may be made without departing from the spirit and scope of the invention.

What is claimed is:

1. An article of manufacture for absorbing and holding oleaginous materials which comprises: a water-absorbent sheet material of cellulosic fibers and a slightly hydrophilic, strongly oleophilic, non-oriented, amorphous nylon uniformly distributed throughout said sheet mate rial in the form of spongy, interconnected particles, said nylon having a moisture regain at 21 C. and relative humidity of from about 3% to 10% by weight.

2. An article of manufacture for absorbing and holding oleaginous materials which comprises: a water-absorbent sheet material of cellulosic fibers and a slightly hydrophilic, strongly oleophilic, non-oriented, amorphousnylon uniformly distributed throughout said sheet material in the form of spongy, inter-connected particles, said nylon being present in the sheet material to the extent of from about 10% to 45% by weight of said sheet ma terial and said nylon having a moisture regain at 21 C.

and 65 relative humidity of from about 4% to 8% by weight.

3. A method of manufacturing a wiping cloth for absorbing and holding oleaginous materials which comprises: forming a solubilizate of a slightly hydrophilic, strongly oleophilic nylon having a moisture regainat' 21 C. and 65% relative humidity of about 2 /z% to- 8% by weight, impregnating a water-absorbent sheet material of cellulosic fibers with said solubilizate, simultaneously coagulating and foaming said nylon whereby it is precipitated on said sheet material in the form of spongy,

interconnected particles of non-oriented, amorphous nylon having a moisture regain at least 15% greater than its original moisture regain and drying said sheet material with the nylon coagulated thereon to form said wiping cloth. 

1. AN ARTICLE OF MANUFACTURE FOR ABSORBING AND HOLDING OLEAGINOUS MATERIALS WHICH COMPRISES: A WATER-ABSORBENT SHEET MATERIAL OF CELLULOSIC FIBERS AND A SLIGHTLY HYDROPHILIC, STRONGLY OLEOPHILIC, NON-ORIENTED, AMORPHOUS NYLON UNIFORMLY DISTRIBUTED THROUGHOUT SAID SHEET MATERIAL IN THE FOR, OF SPONGY, INTERCONNECTED PARTICLES, SAID NYLON HAVING A MOISTURE REGAIN AT 21*C. AND 65% RELATIVE HUMIDITY OF FROM ABOUT 3% TO 10% BY WEIGHT. 